1 Technical Field of the Invention
The present invention relates generally to rotary electric machines. More particularly, the invention relates to a rotary electric machine for a vehicle (e.g., an automotive alternator), which includes a stator that has an outer surface designed to enhance the dissipation of heat generated by operation of the rotary electric machine.
2 Description of the Related Art
In recent years, engine compartments in vehicles have been increasingly required to be small, so as to meet the requirements of adopting a slant-nose design to reduce the vehicle running resistance and securing a more sufficient space in the vehicle compartments. Consequently, the space available for installation of an automotive alternator in the engine compartments has accordingly become small.
Further, the rotational speed of the engines has been reduced for the purpose of improving fuel economy; accordingly, the rotational speed of automotive alternators has also been reduced.
On the other hand, with the increase in electric load caused by, for example, employment of safety control devices, it is required to further increase the power capacity of automotive alternators.
Accordingly, it is required for automotive alternators to be compact, powerful, and non-expensive; thus, it is required for the components of automotive alternators to be highly densely arranged therein.
Moreover, with the recent development in reduction of engine noises, the noises caused by relatively high-speed engine accessories, particularly an automotive alternator, have become noticeable.
As an effort to reduce the automotive alternator noises, Japanese Patent First Publication No. S58-43157 discloses an automotive alternator wherein: a frame encloses the outer periphery of a stator core; the stator core has a plurality of protrusions formed on the outer surface thereof; a coolant flows through the hollow space formed between the inner surface of the frame and the outer surface of the stator core, thus cooling the stator core.
With the above configuration, it is possible to improve the cooling performance of the automotive alternator while reducing the leakage of noises from the automotive alternator to external.
However, at the same time, providing the hollow space for the flow of the coolant makes the automotive alternator redundant. Further, a piping system is necessary for supplying the coolant to the automotive alternator from, for example, an engine radiator; the piping system makes the arrangement of machines or devices in the engine compartment denser and more complex. Furthermore, to prevent leakage of the coolant, it is required to secure high precision of contact surfaces and high reliability of contacting portions in the automotive alternator and in the piping system.